使用变量访问PHP obj

Question

Updating this question...I'm working on a small CMS. The data is held in XML. I'm trying to access the right image field to update the filename and delete the current image.

Script gets variables based on where it was called from. In this case $page = "homes", $elem = "home" and $field = 0. Below is called on an image upload.

if (!empty($_FILES)) {
    $field = $_POST['field'];
    $tempFile = $_FILES['upload']['tmp_name'];
    $targetFile = "img/sections/".$_POST['page']."/";
    $targetFile .= basename($_FILES['upload']['name']);
    if (move_uploaded_file($tempFile,$targetFile)) {
        $file = "spice.xml";
        $load = simplexml_load_file($file);
        $old_img = $load->sections->$page->$elem[$field]['img'];
        $load->sections->$page->$elem[$field]['img'] = $targetFile;
        file_put_contents($file, $xml->saveXML());
        unlink($old_img);
    }
}

This is the structure of the XML file:

<spice>
    <sections>
        <homes>
            <home img="img/sections/home/img1.jpg"/>
            <home img="img/sections/home/img2.jpg"/>
            <home img="img/sections/home/img3.jpg"/>
        </homes>    
    </sections>
</spice>

My problem is that $old_img is giving me a "Cannot use string offset as an array" error. If I replace just the $elem and $field variables with values it all works fine.

Answer 1

PHP is interpreting the [$field] offset as part of the variable $elem and not the entire property $load->sections->$page->$elem , which is probably where your problem lies. Visually, this is what PHP is looking for:

// The character at the 0th ($field) position of 'home' ($elem) is 'h'
'h'['img']

Which causes that error you're seeing because string offsets are strings, not arrays.

Try this instead. Notice the curly braces around $elem .

        $old_img = $load->sections->$page->{$elem}[$field]['img'];
        $load->sections->$page->{$elem}[$field]['img'] = $targetFile;

Answer 2

Alternative code using XPath:

$load = simplexml_load_file($file);
$path=$load->xpath('//sections/'.$page.'/'.$elem);
$path[$field]['img']=$targetFile;